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Oxford - Diversity Of life > The viruses > Flashcards

The viruses Flashcards

1
Q

What type of parasite are viruses

A

Obligate intracellular parasites

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2
Q

Define virion

A

W virus particle that is extracellular and can move from one cell to another

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3
Q

5 methods of studying viruses

A 
Tissue culture 
Physical methods - EM, ultracentifugation
Serology/immunological methods
DNA sequencing
Pathology + transmission studies
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4
Q

What viral structure are those that infect prokaryotic cells

A

Usually have naked capsids

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5
Q

What viral structure are those that infect eukaryotic cells

A

Most often enveloped

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6
Q

Viral capsid

Formed form
Packed with

A

Formed form protein sub units

Packed with viral DNA

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7
Q

What do virions have

A

Molecular receptors that enable recognition and attachment onto host cells

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8
Q

What is the envelope covering the capsid of eukaryotic viruses derived from

A

The host cell

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9
Q

Large virus

A

Mimivirus

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10
Q

Baltimore classification

A

System used to classify viruses based on their manner of mRNA synthesis

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11
Q

How many Baltimore groups are there?

A

7

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12
Q

What three things do Baltimore classification take into account?

A
  1. If viral genome is DNA or RNA
  2. If viral genome is ss or ds
  3. If the sense of a ssRNA is positive or negative
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13
Q

Most common Baltimore classification of viruses that infect bacteria and archaea

A

dsDNA

ssDNA

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14
Q

Most common classification of viruses that infect eukaryotic cells

A

RNA viruses

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15
Q

Viral genomes - DNA (5 things)

A

Reactive - Deoxyribose less reactive due to C-H bonds
Alkaline - DNA stable in alkaline
Grooves - DNA has smaller grooves more resistant to enzymatic attack
Double stranded
Mutation rate - lower

(RAG DM)

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16
Q

Viral genomes - RNA (5 things)

Opposite of DNA
RAG DM
But ribose more reactive due to

A

C-OH bonds

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17
Q

How are viruses phylogenetically analysed

A

Comparing proteins rather than ribosomal RNA because they don’t have ribosomes

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18
Q

Oldest group of viruses appear to be

A

dsRNA

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19
Q

Which viruses may have played a role in transition from RNA to DNA world

A

Retroviruses

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20
Q

Why have some RNA viruses evolved DNA genomes

A

To protect their genomes from cellular ribonucleases

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21
Q

Viroids

A

Small single stranded circular RNAs that don’t have a protein coating (like most viruses).

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22
Q

All known viroids are inhabitants of

A

Angiosperms

23
Q

General bacterial virus life cycle

A
  1. Virions locate cell
  2. Replicate in cell
  3. Leave the cell
24
Q

Take home message about viruses

A

There is huge variety in the way they work (entry strategies, specific things about their life cycles, exit strategies)

25
Q

Pseudolysogeny

XXX

A

Stalled development of a bacteriophage in a host cell

No multiplication of phage genome/replication alongside cell cycle of the host

26
Q

Mollicutes

A

Class of bacteria without a cell wall

27
Q

X

A

Viruses can infect bacteria
Viruses can infect eukaryotic cells
The general life cycle is similar in that they enter the cell, replicate then leave
But in eukaryotes the entry strategies might be more complex

28
Q

What is segmented RNA viruses

A

Viruses in which the genome consists of more than one RNA molecule

(Genome segments can be packaged into a single virion particle or into separate particles)

29
Q

Disadvantages of segmented RNA viruses

A

When 2nor more compatible viruses co infect a cell it enables re combination of their genomes which can have consequences on evolution and immune escape

30
Q

How many segments does influenza virus have

A

8 ssRNA segments

31
Q

What is antigenic shift

A

Two or more different viral strains or two or more different viruses combine to form a new sub type that has a mixture of the surface antigens of the original strains

32
Q

Where do influenza virus mutations often occur

A

HA (haemagglutin) genes
NA (neuraminidase) genes

Which can affect binding or neutralising antibodies from the immune system

33
Q

Why does influenza have pandemic potential

A

Antigenic shift could occur producing a sudden strain which nobody has immunity against and existing vaccines do not work for

34
Q

How does EBV spread

A

Orally

35
Q

What type of virus is EBV and what family does it belong to

A

dsDNA

Herpes family

36
Q

What time of infection does EBV usually form

A

Latent infection

Persists as an episome of circular DNA within the nuclei of infected B cells

37
Q

How can EBV cause cancer

A

Mutations in cells infected with EBV can lead to cancerous changes

38
Q

What are endogenous retroviruses

A

Viral elements in the genome that closely resemble and can be derived from retroviruses

39
Q

What are transposable elements

A

Sequences of DNA that Juno from one location in the genome to another

40
Q

How are transposable elements classified ?

A

Transposons and retro elements

Retroelements: non LTR or LTR

41
Q

Define LTR

A

Long terminal repeat

Classification of retroelement

42
Q

In the human genome what % of retro elements make up the 3 million transposable elements

A

90% transposable elements are retroelements

Other 10% are transposons

43
Q

What are retroelements

A

Endogenous components of eukaryotic genomes that are amble to amplify to new locations in the genome through an RNA intermediate

44
Q

Disadvantage if retroelements

A

Integration could cause harm by disrupting or dis regulating essential genes

45
Q

Paleovirology

A

Study of viruses that existed in the past but are now extinct

46
Q

What are EVEs - endogenous viral elements ?

A

A DNA sequence derived from a virus and present within the germ line of a non viral organism

47
Q

Reticuloendotheliosis virus

A

Can cause running and tumours in poultry

48
Q

Examples of zoonotic disease

A

Influenza from birds and pigs to humans

SARS from bats to humans

49
Q

What does Ebola virus infect

A

Macrophages and epithelial cells

50
Q

Example of a virus infecting a virus

A

APMV large virus in amoeba. Sputnik is a virus that harms APMV replication

51
Q

Summary - viruses are

A

Obligate cellular parasites
Abundant on earth
Affect all living things including other viruses

52
Q

Summary - viruses exhibit a wide diversity of

A

Structures
Genome compositions and mutation rates
Life cycles

53
Q

Summary - viruses have to

A

Spread among hosts
Enter cells
Replicate
Leave the host cell/integrate into genome

54
Q

Large proportion of animal genomes are

A

Of viral origin (have viral sequences in them)

Oxford - Diversity Of life (39 decks)

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